People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Although fever-reducing medication may help against the fatigue, pain, and generally gross circumstances of influenza, it will also drive the spread of the virus, making it a questionable care strategy during the winter months, a new study from McMasters University has found.

Anyone who’s ever been floored by a seasonal spell of the flu knows that a high fever is, for lack of better medical nomenclature, the worst. It turns out, however, that the symptom is a central part of the body’s own defense protocol, and that messing with it ultimately comes to the detriment of everyone around you. With no fever, viral activity goes on unbridled, allowing the infection to claim even more victims.

Don’t Take Your Medication

Dr. David Earn, investigator at the Michael G. DeGroote Institute for Infectious Disease Research and lead author of the study, said in a press release that, ironically, drugs like ibuprofen and acetaminophen may for this reason be viewed as significant factors of disease growth. "Because fever can actually help lower the amount of virus in a sick person's body and reduce the chance of transmitting disease to others, taking drugs that reduce fever can increase transmission,” he explained. “We've discovered that this increase has significant effects when we scale up to the level of the whole population."

He added that the effect is amplified by the common misconception that a person’s fever corresponds to the intensity of his or her illness. "People often take — or give their kids — fever-reducing drugs so they can go to work or school, Earn said. "They may think the risk of infecting others is lower because the fever is lower. In fact, the opposite may be true: The ill people may give off more virus because fever has been reduced."

Boosting Influenza Rates

Earn, who also happens to be a professor of mathematics at McMasters University in Canada, used a mathematical model to estimate the impact of fever-reducing medication on North American flu rates. He and his colleagues found, on average, these drugs drive annual cases up by five percent. This figure may sound small, but on a continental scale, it corresponds to about 1,000 more influenza deaths.

The current study adds to the growing number of efforts to improve national flu prevention and public knowledge about disease control. Another example is the recent New York City mandate whereby all children enrolled in city-licensed day care services and preschools must get seasonal flu shots. While these measures have been praised by organizations like Families Fighting Flu, they have also received excoriating criticism from groups like Autism Action Network, who believes that immunization can lead to autism and other developmental disorders.

That said, it may take years before new guidelines hit municipal health boards across the nation. "Although we have put together the best available estimates for each parameter in our model, we have a long way to go before we can make concrete policy proposals,” co-author Ben Bolker told reporters. "We need more experiments to determine precisely how much reducing fever increases viral shedding in humans and to estimate how much more people spread disease because they are more active in the community when they alleviate their symptoms by taking medication."